Compression control of cascode power amplifiers

1. A power amplifier module comprising:

a power amplifier including a cascode transistor pair, the cascode transistor pair including a first transistor and a second transistor;

a current comparator configured to compare a first base current of the first transistor and a second base current of the second transistor to generate a comparison signal; and

a saturation controller configured to maintain the power amplifier out of saturation based on the comparison signal.

2. The power amplifier module of claim 1 wherein an emitter of the first transistor is coupled to a collector of the second transistor.

3. The power amplifier module of claim 1 wherein the comparison signal indicates that the power amplifier is in a compression state.

4. The power amplifier module of claim 1 wherein the comparison signal indicates a ratio between the first base current and the second base current.

5. The power amplifier module of claim 1 wherein the saturation controller is configured to supply a reference signal to a voltage converter based on the comparison signal, the voltage converter being configured to modify a supply voltage provided to the power amplifier based at least in part on the reference signal.

6. The power amplifier module of claim 1 wherein the saturation controller is configured to supply a reference signal to an impedance matching network based on the comparison signal, the impedance matching network being configured to modify a load impedance of a load line in electrical communication with the power amplifier based at least in part on the reference signal.

7. The power amplifier module of claim 1 wherein the saturation controller is configured to supply a reference signal to an RF attenuator based on the comparison signal, the RF attenuator being configured to modify the amplitude of an RF input signal supplied to the power amplifier based at least in part on the reference signal.

8. The power amplifier module of claim 1 wherein the saturation controller is configured to supply a first reference signal based on the comparison signal to a first operating module and configured to supply a second reference signal based on the comparison signal to a second operating module.

9. The power amplifier module of claim 8 wherein the first operating module includes a voltage converter configured to modify a supply voltage provided to the power amplifier based at least in part on the first reference signal and the second operating module includes an RF attenuator configured to modify the amplitude of an RF input signal supplied to the power amplifier based at least in part on the second reference signal.

10. The power amplifier module of claim 8 wherein the first operating module includes a voltage converter configured to modify a supply voltage provided to the power amplifier based at least in part on the first reference signal and the second operating module includes an impedance matching network configured to modify a load impedance of a load line in electrical communication with the power amplifier based at least in part on the reference signal.

11. The power amplifier module of claim 1 wherein the saturation controller is configured to, based on a power of an RF input signal supplied to the power amplifier, supply a first reference signal based on the comparison signal to a voltage converter configured to modify a supply voltage provided to the power amplifier based at least in part on the first reference signal or supply a second reference signal to an RF attenuator configured to modify the amplitude of the RF input signal based at least in part on the second reference signal.

12. The power amplifier module of claim 1 wherein the saturation controller is configured to, based on a number of wireless devices in a particular geographical area, supply a first reference signal based on the comparison signal to a voltage converter configured to modify a supply voltage provided to the power amplifier based at least in part on the first reference signal or supply a second reference signal to an RF attenuator configured to modify the amplitude of an RF input signal supplied to the power amplifier based at least in part on the second reference signal.

13. A method of maintaining a power amplifier out of saturation, the method comprising:

comparing a first base current of a first transistor of a cascode power amplifier and a second base current of a second transistor of the cascode power amplifier; and

maintaining the cascode power amplifier out of saturation by modifying an operating characteristic of the cascode power amplifier based on the comparison, the operating characteristic including a supply voltage provided to the cascode power amplifier, an amplitude of an RF input signal supplied to the cascode power amplifier, or a load impedance of a load line in electrical communication with the cascode power amplifier.

14. The method of claim 13 wherein comparing the first base current and the second base current includes determining a ratio of the first base current and the second base current, maintaining the cascode power amplifier out of saturation including modifying the operating characteristic based on the ratio.

15. The method of claim 14 wherein comparing the first base current and the second base current includes determining that the ratio of the first base current and the second base current exceeds a threshold, maintaining the cascode power amplifier out of saturation including modifying the operating characteristic based on the determination that the ratio of the first base current and the second base current exceeds the threshold.

16. The method of claim 13 further comprising modifying a second operating characteristic of the cascode power amplifier based on the comparison signal, the second operating characteristic including another of the supply voltage, the amplitude of the RF input signal, or the load impedance.

17. The method of claim 13 further comprising selecting the operating characteristic based on an operating environment of the wireless device.

18. The method of claim 13 further comprising selecting the operating characteristic based on a command from a base station.

19. A wireless device comprising:

a transceiver configured to generate an RF input signal;

a power amplifier module including a power amplifier, a current comparator, and a saturation controller, the power amplifier being configured to amplify the RF input signal to generate an RF output signal, the power amplifier including a cascode transistor pair, the cascode transistor pair including a first transistor and a second transistor, the current comparator being configured to compare a first base current of the first transistor and a second base current of the second transistor to generate a comparison signal, the saturation controller configured to maintain the power amplifier out of saturation based on the comparison signal; and

an antenna in communication with the power amplifier module, the antenna configured to transmit the RF output signal.

20. The wireless device of claim 19 , the saturation controller being configured to maintain the power amplifier out of saturation by providing a reference signal to one or more of a voltage converter, an RF attenuator, or an impedance matching network, the voltage converter being configured to modify a supply voltage provided to the power amplifier based at least in part on the reference signal, the RF attenuator being configured to modify the amplitude of the input RF signal based at least in part on the reference signal, and the impedance matching network being configured to modify a load impedance of a load line in electrical communication with the power amplifier based at least in part on the reference signal.